1. Field
One embodiment of the invention relates to a video signal processor detecting a pulldown signal of a movie or the like generated using a 2:2 pulldown, and a video signal processing method.
2. Description of the Related Art
Conventionally, an interlaced-to-progressive scanning converter generating an interpolation signal based on a detection result obtained by detecting an image movement in the video signal has been known for converting an interlaced scanning video signal into a progressive scanning video signal, in order to prevent an image quality deterioration in a moving image.
In the conventional interlaced-to-progressive scanning converter, it is concerned that an image quality of a moving image might be deteriorated during processing thereof. It has been known that the video signal of which frames or fields are generated in a constant pattern can be converted into a progressive scanning video signal without deteriorating the image quality. An interlaced scanning video signal generated using a 2:2 pulldown or 2:3 pulldown has a regularity such that two or three fields generated from a same frame are consecutive. Hence, if the pattern of the consecution is known, it is possible to use the sequential fields generated from the same frame for the conversion. Accordingly, the interlaced scanning signal can be converted into the progressive scanning signal by a field interpolation, regardless of whether the image being a still image or a moving image.
However, the conventional interlaced-to-progressive converter falsely determines an input video signal as a video signal using 2:2 pulldown (hereinafter, referred to as 2:2 pulldown signal) as in the following.
Suppose that a video contains an image having a steep (that is to say, a luminance difference being large) edge (an edge portion) along a horizontal direction of the image, and suppose that the image shifts to a vertical direction of the image at a constant speed (such image is called “an edge image moving at a constant speed” in the following). For example, such edge image moving at a constant speed corresponds to a rectangular image moving from down to up at a constant speed with even number pixels per field.
In such video signal, a difference between signal levels and the like of fields increases/decreases by every one field. Therefore, such video signal obtains the same pattern as that of the 2:2 pulldown signal when the difference is eliminated. Accordingly, when a video signal contains the edge image moving at a constant speed, such video signal is falsely determined as the 2:2 pulldown signal.
Conventionally, there has been known an interlaced-to-progressive scanning converter disclosed in, for example, Japanese Patent Application Publication (Kokai) No. 2004-297476, which avoids the aforementioned false determination.